This invention relates to arrangements and methods for controlling deployment of a vehicular occupant restraint device utilizing a plurality of crash sensors, at least one of which is mounted in the crush zone of the vehicle and another of which is mounted outside of the crush zone. In particular, this invention relates to a sensor that covers a wide area of the vehicle and is mounted in the front of the crush zone and measures the velocity change of the crush zone early in the crash.
This invention also utilizes improvements on the inventions disclosed in U.S. Pat. No. 4,995,639 (Breed) and a full discussion of the background of this general type of sensor is disclosed in that patent and included herein by reference.
In Society of Automotive Engineers (SAE) paper No. 930650 entitled xe2x80x9cA Complete Frontal Crash Sensor Systemxe2x80x94Ixe2x80x9d, by Breed et al., which is incorporated herein by reference, the authors conclude that airbag crash sensors mounted in the crush zone are necessary for the proper sensing of airbag-required frontal crashes. They also conclude that such sensors should sense crashes to all portions of the front of the vehicle and that sensors which sense the crush of the vehicle are preferred. The theory of crush sensing is presented in the above-referenced U.S. patents and patent applications and in SAE paper No. 920122 entitled, xe2x80x9cPerformance of a Crush Sensor for Use with Automotive Airbag Systemsxe2x80x9d, by Breed et al, which is incorporated herein by reference.
The tape switch and rod-in-tube crush sensors described in the above-referenced U.S. patents and patent applications have performed successfully on various staged vehicle frontal crashes into barriers and poles. These sensors are generally not sufficient for sensing side impacts as discussed in Breed, D. S., Sanders, W. T. and Castelli, V., xe2x80x9cSensing Side Impactsxe2x80x9d, Society of Automotive Engineers (SAE) paper No. 940561, 1994, however, they can be successful when used in conjunction with a passenger compartment mounted electronic sensor or as a safing sensor. Similarly, they are also being considered when a deployable device, such as an airbag, is used for rear impacts.
Three types of sensors have been widely used to sense and initiate deployment of an air bag passive restraint system. These sensors include an air damped ball-in-tube sensor such as disclosed in U.S. Pat. Nos. 3,974,350, 4,198,864, 4,284,863, 4,329,549 and 4,573,706 (all in the name of Breed), a spring mass sensor such as disclosed in U.S. Pat. Nos. 4,116,132 and 4,167,276 (both in the name of Bell) and an electronic sensor such as is now part of several air bag systems. Each of these sensors has particular advantages and shortcomings that were discussed in detail in U.S. Pat. No. 4,995,639 referenced above.
The use of tape or ribbon switch technology as a crush switch was also disclosed in the ""639 patent. Further research has shown that an improvement of this particular implementation of the invention has significant advantages over some of the other implementations since the switch can be easily made long and narrow and it can be made to respond to bending. In the first case, it can be designed to cover a significant distance across the vehicle which increases the probability that it will be struck by crushed material or bent as the crush zone propagates rearward in the vehicle during a crash. In the second case, it can be made small and located to sense the fact that one part of the vehicle has moved relative to some other part or that the structure on which the sensor is mounted has deformed.
Other crush zone mounted crash sensors including crush switch designs where the width and height dimensions are comparable, must either be large and thus heavy, expensive and difficult to mount, or there is a possibility that the randomly shaped crushed material which forms the boundary of the crush zone will bridge the sensor resulting in late triggering. This crushed material frequently contains holes, wrinkles or folds or portions that may even be displaced or torn out during the crash with the result that it is difficult to guarantee that a particular small area where the sensor is mounted will be struck early in the crash.
A significant improvement results, therefore, if the sensor can stretch across more of the vehicle or if it can determine that there has been relative motion or deformation of a portion of the vehicle on which the sensor is mounted. The improved sensors described herein are small in height and thickness but can extend to whatever length is necessary to achieve a high probability of a sensor triggering on time in a crash.
It has been found that conventional designs of tape or ribbon switches have the drawback that the force required to close the switch is very small compared with the forces which are normally present in automobile crashes. During routine maintenance of the vehicle, the normal tape switch may be damaged or otherwise made to close and remain closed, with the result that later, when the vehicle encounters a pot hole or other shock sufficient to cause the arming sensor to close, an inadvertent air bag deployment can result. Similarly, if the tape switch is mounted on the front of the radiator support, which is a preferred mounting locating for crush zone sensors, hail, heavy rain, stones or other debris from the road might impact the tape switch and cause a momentary closure or damage it. If this happens when the vehicle experiences a shock sufficient to cause the arming sensor to close, an inadvertent air bag deployment might also occur. The force typically required to close a tape switch is less than one pound whereas tens of thousands of pounds are required to stop a vehicle in a crash and local forces greatly in excess of 20 pounds are available to actuate a sensor during a crash.
The present invention seeks to eliminate these drawbacks through the use of a tape switch, rod-in-tube or coaxial cable design that requires either a large force to actuate or a bending of the device due to structural deformation as explained below.
In 1992, the assignee of the current invention published a paper titled xe2x80x9cA Critique of Single Point Sensingxe2x80x9d, SAE 920124, which is incorporated herein by reference, where the authors demonstrate that there is insufficient information in the non-crush zone of the vehicle to permit a decision to be made to deploy an airbag in time for many crashes. The crash sensors described herein and in the patents and patent applications referenced above, provide an apparatus and method for determining that the crush zone of the automobile has undergone a particular velocity change. This information can be used by itself to make the airbag deployment decision. As airbag systems become more sophisticated, however, the fact that the vehicle has undergone a velocity change in the crush zone can be used in conjunction with an electronic sensor mounted in the passenger compartment to not only determine that the airbag should be deployed but an assessment of the severity of the crash can be made. In this case, the front crush zone mounted sensor of the type disclosed herein can be used as an input to an electronic algorithm and thereby permit a deployment strategy based on the estimated severity of the accident. Although the sensors described herein are one preferred approach of providing this capability, the sensors disclosed in the above referenced patents would also be suitable. Alternately, in some cases, sensors of another design can fulfill this function. Such sensors might be based on the electromechanical technologies such as the ball-in-tube sensor described in U.S. Pat. No. 4,900,880 or in some cases even electronic sensors could be used as crush zone mounted sensors for this purpose.
Other technical papers which provide pertinent background information to this invention include:
1. Breed, D. S., Castelli, V. xe2x80x9cProblems in Design and Engineering of Air Bag Systemsxe2x80x9d, Society of Automotive Engineers paper No. 880724, 1988.
2. Breed, D. S., Castelli, V. xe2x80x9cTrends in Sensing Frontal Impactsxe2x80x9d, Society of Automotive Engineers paper No. 890750, 1989.
3. Castelli, V., Breed, D. S. xe2x80x9cTrends in Sensing Side Impactsxe2x80x9d, Society of Automotive Engineers paper No. 890603, 1989.
4. Breed, D. S., Castelli, V. and Shokoohi, F. xe2x80x9cAre Barrier Crashes Sufficient for Evaluating Air Bag Sensor Performance?xe2x80x9d, Society of Automotive Engineers paper No. 900548, 1990.
5. Breed, D. S., Sanders, W. T. and Castelli, V. xe2x80x9cA Critique of Single Point Crash Sensingxe2x80x9d, Society of Automotive Engineers paper No. 920124, 1992.
6. Breed, D. S., Sanders, W. T. and Castelli, V. xe2x80x9cPerformance of a Crush Sensor for Use with Automobile airbag Systemsxe2x80x9d, Society of Automotive Engineers paper No. 920122, 1992.
7. Shokoohi, F., Sanders, W. T., Castelli, V., and Breed, D. S. xe2x80x9cCross Axis Specifications For Crash Sensorsxe2x80x9d, Automotive Technologies International Report, ATI 12004, 1991. Society of Automotive Engineers paper No. 930651, 1993.
8. Breed, D. S., Sanders, W. T. and Castelli, V. xe2x80x9cA complete Frontal Crash Sensor Systemxe2x80x94Ixe2x80x9d, Society of Automotive Engineers paper No. 930650, 1993.
9. Breed, D. S. and Sanders, W. T. xe2x80x9cUsing Vehicle Deformation to Sense Crashesxe2x80x9d, Presented at the International Body and Engineering Conference, Detroit Mich., 1993.
10. Breed, D. S., Sanders, W. T. and Castelli, V., xe2x80x9cA complete Frontal Crash Sensor Systemxe2x80x94IIxe2x80x9d, Proceedings Enhanced Safety of Vehicles Conference, Munich, 1994, Published by the U.S. Department of Transportation, National Highway Traffic Safety Administration, Washington, D.C.
11. Breed, D. S., Sanders, W. T. and Castelli, V., xe2x80x9cSensing Side Impactsxe2x80x9d, Society of Automotive Engineers paper No. 940561, 1994.
12. Breed, D. S., xe2x80x9cSide Impact Airbag System Technologyxe2x80x9d, Presented at the International Body and Engineering Conference, Detroit Mich., 1994.
13. Breed, D. S., xe2x80x9cA Smart Airbag Systemxe2x80x9d, Presented at the 16th International Technical Conference on the Enhanced Safety of vehicles, Windsor, Canada, Paper Number 98 S5 O 13, 1998.
Other relevant prior art includes U.S. Pat. No. 3,859,482 to Matsui, which will now be discussed in some detail. Matsui shows various devices which respond to the force (pressure using Matsui""s terminology) which accompanies a vehicle frontal crash when material in the extreme front of the vehicle, or the impacting object itself, impacts the force detecting device. Matsui also mentions, but does not illustrate, the use of his force detectors on the rear and the side of the vehicle. The Matsui devices discriminate crashes based on the magnitude of this force on the detecting device, which as stated in the patent, are in the order of tons (metric). Many devices are described in Matsui however the following generalizations apply:
1. The Matsui sensors. are mechanical pressure (force) detecting devices. This is stated in the title of the patent and throughout, there is only discussion of pressure being applied directly to the sensor. Except in those cases where a tape switch or a rope is used as the forwardmost point on the vehicle, there is always associated with the device a xe2x80x9cPresser Memberxe2x80x9d whose function is to apply force directly to the sensor. Most importantly, this is a device which determines the severity of a crash based on force where the force is in the order of metric tons.
As discussed in greater detail below, the devices disclosed in the instant invention are displacement and velocity sensors not force sensors. They do not require tons of force to actuated and a xe2x80x9cPresser Memberxe2x80x9d is not required or in general used.
2. The Matsui sensors are used in combination with a high level deceleration detector. In all cases, the Matsui sensor is used in conjunction with an acceleration sensor. This sensor is a low level discriminating sensor which is different from the safing sensor used on most current airbag systems. The difference between these types of sensors is that the Matsui sensor is not used alone to discriminate the crash, that is to determine whether the crash requires deployment of an airbag. An additional discriminating sensor is required. By contrast, in conventional airbag systems, a safing or arming sensor is used to guard against electrical shorts in the sensor perhaps caused by vehicle maintenance. The safing sensor will trigger on pothole impacts for example. It is not intended to provide information as to the severity of the crash. This is not the case in the Matsui acceleration sensor which is used in series with a force sensor. This is clear by the illustrated embodiment in FIG. 29 which shows that the deceleration sensor requires a value of acceleration to trigger which is shown to be a substantial percent of the peak deceleration of curve A which is on the order of about 40 G""s (see for example FIG. 1 of reference 1 above). In contrast, typical safing or arming sensors trigger on a deceleration of less than about 2 G""s.
Again, as will be discussed in detail below, in contrast, the sensors of the present invention are discriminating sensors and do not require a high level deceleration sensor or any deceleration sensor for that matter, but can be used with such a sensor in some implementations. As the sensors of this invention are used as discriminating sensors, a low level safing or arming sensor can optionally be used to provide electrical isolation of the inflator initiator so that momentary electrical shorts do not cause deployment of the airbag.
3. In many illustrations of the Matsui devices a frangible system is used. In one case, for example, a wire inside a glass tube, or a glass rod or tube which has been plated with silver, is used. In some of these cases, a sensor design is illustrated which is substantially longer than it is thick or wide. In this manner, the sensor can extend across a significant portion of the vehicle in much the same way that the rod-in-tube or coax sensors of the instant invention are implemented. These frangible sensors trigger by being broken, usually by means of a xe2x80x9cPresser Memberxe2x80x9d and to thereby break an electric circuit.
As discussed below, in contrast, the sensors of this invention are not frangible and function by crushing or bending not by breaking and the output is in general not a switch closure but an impedance versus time function that permits the crush velocity to be determined.
4. Due to the requirement that tons of force are needed to trigger the Matsui sensor, rigid mounting thereof is a requirement. This is particularly important at the place on the sensor where triggering is intended to occur.
As set forth below, in contrast, the sensors of this invention sense a crash by crushing or be bending and therefore need not in general be rigidly mounted to the extent that they support more than a few hundred pounds.
5. Tape switch implantation uses pressure actuated tape switches not those designed to by actuated by bending. Matsui explicitly states that the tape switch implementations disclosed are actuated by pressure (column 26, lines 20-23).
As discussed below, the sensors of the instant invention measure the crush velocity by crushing or bending. Also the sensors of this invention are not in general switches but are velocity change measuring devices.
6. The elongated sensors illustrated by Matsui are either frangible, pressure sensing tape switches, or sensors made by stretching a line or rope. All of these designs differ significantly from the rod-in-tube or coaxial cable sensors of the instant invention. The remaining sensors disclosed are all point sensors which trigger when tons of force are applied to the sensor surface. In none of these cases is a sensor designed to function through a measurement of impedance change or to detect a change in velocity suggested.
7. In spite of the large potpourri of sensor designs disclosed, all of which have serious technical deficiencies, nowhere does Matsui suggest a rod-in-tube or coaxial cable geometry of the sensor. The rod-in-tube and coaxial cable geometries permits the sensor to be arbitrarily formed so that it covers all portions of the vehicle that are likely to be involved in a crash. In contrast, the elongated sensors of Matsui are typically shown mounted onto the bumper (erroneously designated as the fender) or immediately behind the bumper. An observation of frontal impacts shows that in approximately 30% of frontal airbag required accidents the bumper is not impacted. Thus, for these cases the Matsui sensor would not trigger.
For the purposes herein, the crush zone is defined as that part of the vehicle which crushes or deforms during a particular crash. This is a different definition from that used elsewhere and in particular in the above referenced technical papers. Also for the purposes herein, the terminology Crush Sensing Zone, or CSZ, will be used to designate that portion of the vehicle which is deformed or crushed during a crash at the sensor required trigger time. The sensor required trigger time is considered the latest time that a crash sensor can trigger for there to be sufficient time to deploy the airbag. This is determined by the airbag system designers and is a given parameter to the sensor designer for a particular crash. Naturally, there will be a different required sensor triggering time for each crash, however, it has been found, as reported in the above references, that the CSZ is remarkably constant for all crashes of the same type.
For example, the CSZ is nearly the same for all frontal barrier crashes regardless of the velocity of the crash. The same is true for 30 degree angle barrier crashes although the CSZ is different here than for frontal barrier crashes. Remarkably, and unexpectedly, it has also been found that when all frontal crashes at all different velocities are taken into account, the CSZ rearmost boundary becomes an approximate three dimensional surface lying mostly within the engine compartment of the vehicle, typically about ten to twelve inches behind the bumper at the center, and extending backward when crashes outside of the rails are considered. Finally, if a sensor is placed on this CSZ surface so that it is higher than the bumper level on the ""sides of the vehicle and lower in the vehicle center, as shown in FIG. 1 herein, it will do a remarkable job at discriminating between airbag required and non-deployment crashes and still trigger by the sensor required triggering time and before other sensors of comparable sensitivity. Naturally, this system is not perfect, however, it has been shown to do a better job than any other sensor system now in use.
It was this discovery which provided a basis for the subject matter described in U.S. Pat. No. 4,995,639 and then to the rod-in-tube sensor described in U.S. Pat. No. 5,441,301. During the process of implementing the rod-in-tube sensor, it was found that the same theory applies to rear impacts and that rod-in-tube sensors also have applicability to side impact sensing, although the theory is different.
In U.S. Pat. No. 5,694,320 (Breed), incorporated by reference herein, the theory of sensing rear impacts is presented and it is concluded that an anticipatory sensing system is preferred. This is because many people suffer whiplash injuries at rather low velocity impacts and if an inflatable restraint is used, the repair cost may be significant. To protect most people from whiplash injuries in rear impacts, therefore, a resetable system is preferred. The argument on the other side is that if the headrest is properly positioned, it will take care of all of the low velocity impacts and, therefore, an airbag can be used and reserved for the high velocity impacts where a crush sensing crash sensor would be used. The rod-in-tube sensor disclosed herein is, therefore, ideal for use with a deployable headrest mounted airbag for the same reasons that it is a good sensor for sensing frontal impacts. Since the rear of a vehicle typically has about one third of the stiffness of the vehicle front, electronic sensors will have even a tougher time discriminating between trigger and non-trigger cases for rear impacts. As disclosed in references 5 and 9 above, it is the soft crashes which are the most difficult for electronic sensors to sense in time.
Crush sensing crash sensors are not ideal for sensing side impacts alone, although the Volvo side impact system uses such a sensing system. This is because the sensing time is so short that there is virtually no crush (about two inches) at the time that the airbag must be deployed. Since there is very little signal out of the crush zone where electronic sensors are mounted, electronic sensors alone are not able to discriminate airbag required crashes from other crashes not requiring airbag deployment. The combination of the two sensors, on the other hand, can be used to provide a reliable determination. The crush sensor determines that there has been two inches of crush and the electronic sensor determines that the acceleration signal at that time is consistent with there being an airbag required crash. Thus, although they cannot be reliably used alone as a discriminating sensor for side impacts, the combined system does function properly.
An alternate use of the crush sensor such as the rod-in-tube sensor in side impacts is as a safing sensor. In this role, it merely determines that a crash is in progress and the main discriminating function is handled by the velocity sensing sensors such as disclosed in U.S. Pat. No. 5,231,253 (assigned to the current assignee).
The rod-in-tube or coaxial cable crush velocity sensing crash sensors solve this side impact problem and thus applications include frontal, side and rear impacts, where in each case they enjoy significant advantages over all other crash sensing technologies. Examples of the preferred implementations are described in the paragraphs below.
With respect to other prior art related to the invention, Peachey (U.S. Pat. No. 4,060,705) describes a pressure actuated continuous switch which designed to actuate about its entire circumference, i.e., in all directions. The switch of the embodiment in FIG. 1 of Peachey includes a central, inner conductor 1, an insulating thread 2 helically wound around the conductor 1 and an outer conductor 3, all housed within a sheath of insulating material 4. The switch in the embodiment of FIG. 2 includes a central, inner conductor 1, an insulating thread 2 helically wound around the conductor 1, a sheath of graphite-loaded plastic 5 surrounding the thread 2, an outer conductor 3 surrounding the sheath 5 and a sheath of insulating material 4 surrounding the outer conductor 3. The switch in these embodiments is actuated when pressure is applied to the switch so that the outer conductor (FIG. 1) or sheath 5 (FIG. 2) is deflected to cause it to make contact with the inner conductor 1 and thereby establish electrical contact between the inner and outer conductors 1, 3, in the embodiment of FIG. 2 through the sheath 5. In view of the helical winding of the insulating thread 2 around the inner conductor 1, these switches can be actuated by bending at almost all locations (except for an impact into a location where the insulating material 2 is interposed between the conductors 1, 3).
U.S. Pat. No. 2,437,969 to Paul describes a deformable switch 10 in the form of a tube that is actuatable at all circumferential points along its length. The tube includes a central coil of electrically conducting wire 12, a braided electrically conducting, metal tube 11 and insulating separators 13 spaced at discrete locations along the length of the switch 10 to support the tube 11 around the wire 12. The switch is actuatable at all circumferential locations along the length of the tube, except for the locations at which the insulating separators 13 are located. In use, when pressure is applied to the tube 11, it deforms at the location at which pressure is applied thereby coming into contact with the wire 11 and causing a circuit to close.
U.S. Pat. No. 5,322,323 to Ohno et al. describes to a collision sensing system for an airbag including collision sensors and acceleration sensors wherein deployment of the airbag is based on a signal from the collision sensors and an analysis of the output from the acceleration sensors.
U.S. Pat. No. 5,797,623 to Hubbard describes an allegedly unique side impact sensor based on a piezoelectric film. The sensor essentially measures the energy of impact providing the entire force applied to the film, which would not in general be the case. The velocity of the impacting vehicle can be determined again if the sensor absorbs the entire force and if the mass of the impacting object is known. Since neither of these can be assumed, the device will not provide a measurement of the impacting velocity and therefore at best can act as an impact-sensing switch with some discriminating capability.
The prior art crush zone mounted sensors therefore are either force sensing switches (Matsui) or piezoelectric film sensors (Hubbard) mounted in the forwardmost part of the crush zone, are velocity change sensors (ball-in-tube) mounted at the rear most edge of the CSZ or crush sensing switches also mounted at the rear most edge of the CSZ. Sensors mounted at the rear most edge of the CSZ by nature will trigger at the last possible moment when the airbag must deploy based on the seating position of the average male occupant. It is known that currently up to about 70% of vehicle occupants sit closer to the airbag than the average male and therefore such sensors trigger airbag deployment late for such occupants placing them at risk of being injured by the airbag. Heretofore, there are no velocity change sensors that are mounted in the forward part of the crush zone where the velocity change of the crash can be determined early in the crash and the airbag deployed early. There is thus a need for such a crash sensor.
Principle objects and advantages of this invention are:
1) To provide a single sensor which will sense all airbag desired crashes involving the either the front, rear or a side of the vehicle.
2) To provide a sensor which is much longer than it is wide or thick thus permitting it to sense crashes over a large area while occupying a relatively small space.
3) To provide a sensor that can be easily shaped so to be properly placed in front of the CSZ boundary across the entire front, side or rear of the vehicle.
4) To provide a crush sensor where the rate of deformation required to trigger the sensor can be measured along the length of the sensor.
5) To provide a sensor to be used in conjunction with an electronic passenger compartment mounted sensor which will trigger on all of the airbag desired crashes which are missed by the electronic passenger compartment mounted sensor alone for either frontal, side or rear impacts.
6) To provide a simple and convenient sensor system consisting of a single discriminating sensor mounted in front of the CSZ boundary and a single arming sensor mounted in the passenger compartment for frontal, side and/or rear impacts.
7) To provide a crush velocity change crash sensor which functions when a portion of the vehicle where the sensor is mounted is displaced, deformed or otherwise bends or buckles.
8) To provide a hermetically sealed crush velocity sensing crash sensor.
9) To provide a small, inexpensive, yet highly reliable crash velocity change sensor.
10) To provide an arrangement for a vehicle including a crush zone-mounted discriminating sensor (which provides information about the reaction of the crush zone to a crash, such as the crush of the crush zone, the velocity change of the crush zone resulting from the crash and the acceleration of the crush zone resulting from the crash) in series with a passenger compartment-mounted discriminating sensor to permit a better discrimination between air bag desired and not desired crashes such as animal impacts.
11) To provide an arrangement for a vehicle including a crush zone-mounted discriminating sensor as input to an electronic passenger-compartment discriminating sensor to permit a change in the sensor algorithm, or triggering parameters, based of the output of the crush zone discriminating sensor to improve the performance of the electronic sensor.
A preferred embodiment of the sensor of this invention uses the velocity of the crushing of the vehicle as a measure of the severity of the crash as is the case with the ball-in-tube sensor of U.S. Pat. No. 4,900,880, for example. However, a key teaching of this invention is also the combination of forward or satellite sensors in the crush zone and a non-crush zone sensor and how that combination improves the overall performance of the sensor system.
In one preferred embodiment of the invention, a coaxial cable stretches from the driver side door near the B-pillar through the A-pillar, across the front of the vehicle and into the passenger side door. A signal having a frequency on the order of about 10 megahertz is imposed on the cable, which frequency is selected so that approximately the cable is approximately one wavelength long (thus the frequency could vary depending on the length of the cable). The cable is terminated at the far end with a known resistance. Under normal operation, the wave travels. down the cable and reflects off of the end and returns in phase with the transmitted pulse. If, however, the cable is compressed along its length a reflected wave will be returned that is out of phase with the transmitted wave. By comparing the phase of the reflected wave with the transmitted wave, the location of the compression can be determined and by comparing the magnitude of the reflection, the amount of compression can be determined. By measuring the amount of compression over time, the velocity of compression can be found. Thus, the location of the impact and the crush velocity (which can be considered a function of the velocity of compression) can both be determined by this sensor for both side and frontal impacts. A similar sensor could be designed for use in sensing side and rear impacts.
More generally, a crash sensor arrangement for determining whether the crash involving the vehicle requires deployment of the occupant restraint device comprises an elongate sensor arranged in the crush zone to provide a variable impedance as a function of a change in velocity of the crush zone and a processor for measuring the impedance of the sensor or a part thereof at a plurality of times to determine changes in the impedance of the sensor or part thereof. The processor provides a crash signal for consideration in the deployment of the occupant restraint device based on the determined changes in impedance of the sensor or part thereof The sensor can have a U-shaped portion extending along both sides of the vehicle and across a front of the vehicle, and thus substantially completely between opposed longitudinal edges of a door of the vehicle.
In the embodiment wherein the sensor comprises a coaxial cable, an electromagnetic wave generator generates electromagnetic waves and feeds the waves into the cable and the processor is preferably embodied in an electronic control module coupled to the electromagnetic wave generator. The electromagnetic wave generator preferably feeds electromagnetic waves into the cable having a wavelength on the same order as a length of the cable. In the alternative, the sensor can comprise parallel strips of conductive material spaced apart from one another in the absence of deformation of the crush zone and arranged to contact one another during deformation of the crush zone. The contact strips are positioned so as to be compressed during deformation of the crush zone whereby such compression causes changes in impedance of the sensor.
Another crash sensor arrangement for determining whether the crash involving the vehicle requires deployment of the occupant restraint device comprises a first discriminating crash sensor mounted outside of the crush zone of the vehicle and structured and arranged to trigger by means other than crush of the crush zone of the vehicle, and a second discriminating crash sensor coupled to the first sensor and mounted in the crush zone of the vehicle. The second sensor provides a signal representative of a velocity change of the crush zone during the crash to the first sensor. The first sensor receives the signal representative of the velocity change of the crush zone of the vehicle to the crash from the second sensor, considers whether triggering of the first sensor should be modified based on the velocity change of the crush zone of the vehicle to the crash provided by the second sensor and if so, modifies triggering of the first sensor. The first sensor may consider whether to modify its sensitivity based on the velocity change of the crush zone of the vehicle to the crash. The first sensor can be designed to trigger based on a reaction of the entire vehicle or a part of the vehicle other than the crush zone of the vehicle to the crash and/or may be a discriminating electronic sensor arranged to trigger based on at least one of acceleration of the vehicle and a change in velocity of the vehicle. The second sensor may be the coaxial cable sensor described above in which case, the arrangement includes the additional components, e.g., the electromagnetic wave generator.
Preferred embodiments of the invention are described herein and unless specifically noted, it is the applicant""s intention that the words and phrases in the specification and claims be given the ordinary and accustomed meaning to those of ordinary skill in the applicable art(s). If applicant intends any other meaning, he will specifically state he is applying a special meaning to a word or phrase.
Likewise, applicant""s use of the word xe2x80x9cfunctionxe2x80x9d here is not intended to indicate that the applicant seek to invoke the special provisions of 35 U.S.C. xc2xa7112, sixth paragraph, to define his invention. To the contrary, if applicant wishes to invoke the provisions of 35 U.S.C. xc2xa7112, sixth paragraph, to define his invention, he will specifically set forth in the claims the phrases xe2x80x9cmeans forxe2x80x9d or xe2x80x9cstep forxe2x80x9d and a function, without also reciting in that phrase any structure, material or act in support of the function. Moreover, even if applicant invokes the provisions of 35 U.S.C. xc2xa7112, sixth paragraph, to define his invention, it is the applicant""s intention that his inventions not be limited to the specific structure, material or acts that are described in the preferred embodiments herein. Rather, if applicant claims their inventions by specifically invoking the provisions of 35 U.S.C. xc2xa7112, sixth paragraph, it is nonetheless his intention to cover and include any and all structure, materials or acts that perform the claimed function, along with any and all known or later developed equivalent structures, materials or acts for performing the claimed function.
Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.